Catheter ablation of atrioventricular junction using radiofrequency current in 17 patients. Comparison of standard and large-tip catheter electrodes

Emerging Technologies for Pulmonary Vein Isolation

Atrial fibrillation is the most common sustained cardiac arrhythmia and is associated with considerable morbidity and mortality. Electrically isolating the pulmonary veins from the left atrium by catheter ablation is superior to antiarrhythmic drug therapy for maintaining sinus rhythm, but its success varies depending on multiple factors, including arrhythmic burden. Although procedural outcomes have improved over the years, further gains are limited by a seemingly zero-sum relationship between effectiveness and safety, which is largely a product of the available technologies. Current energies used to create contiguous, transmural, and durable atrial lesions can result in serious complications if they reach the esophagus or phrenic nerve, for instance—structures that can be adjacent to the atrial myocardium, often within millimeters of the energy source. Consequently, high rates of pulmonary vein-left atrium reconnections are consistently seen in clinical studies and in clinical practice as operators appropriately forgo ablation effectiveness to protect patients from harm. However, as ablative technologies evolve to circumvent this stalemate, safer, and more effective pulmonary vein isolation seems increasingly realistic. Furthermore, the innovative nature of these technologies raises the prospect of markedly improved procedural efficiency, which could increase patient comfort, reduce operator occupational injuries, and enhance the use of health resources—all of which are increasingly important considerations particularly as the demand for catheter ablation for atrial fibrillation continues to rise. We herein review 3 promising candidate ablation technologies with the potential to revolutionize the management of patients with atrial fibrillation: electroporation (pulsed-field ablation), expandable lattice-tip radiofrequency ablation/electroporation, and ultra-low temperature cryoablation.

Acute and long-term outcomes of left-sided atrioventricular node ablation in patients with atrial fibrillation

PURPOSE

To present our experience regarding acute and long-term outcomes of left-sided atrioventricular node (AVN) ablation in patients with atrial fibrillation (AF).

METHODS

A total of 47 patients with AF in whom left-sided AVN ablation via retroaortic approach as a first-line approach were enrolled in this retrospective study. Indications for AVN ablation were high ventricular rate refractory to medical therapy, inappropriate implantable cardioverter defibrillator (ICD) shocks, or loss of cardiac resynchronization therapy (CRT) pacing. Both acute and long-term outcomes were assessed for all participants.

RESULTS

Left-sided AVN ablation was successfully performed in 46/47 (98%) patients without any procedural complication. In the remaining 1 patient (2%), right-sided AVN ablation was performed. No mortality was observed within 30 days of the procedure. Upgrade to CRT was performed in 9 (19%) of the patients. During the median 22.5 months of follow-up, all-cause mortality was 25%. Device interrogations on the last clinical visit revealed complete AV block and intrinsic ventricular rate of < 40 bpm in all patients.

CONCLUSION

Left-sided AVN ablation is a safe and effective procedure without recurrence during long-term follow-up.

[Catheter ablation of cardiac arrhythmias : Forms of energy and biophysical principles]

Catheter ablation of cardiac arrhythmias has evolved over the years and has become a cornerstone in the modern treatment of various supraventricular and ventricular arrhythmias. The goal of ablation is to permanently damage myocardium that is critically involved in the individual arrhythmia mechanism. Different catheters and forms of energy are available. Radiofrequency (RF) ablation is most common. Application of an alternating current at the catheter tip induces heating of tissue and, thus, leads to ablation of a targeted arrhythmogenic substrate. High temperatures (>70 °C at the catheter tip and >95 °C within the tissue) bear the risk of coagulum formation and steam pops and should be avoided, which limits power application. The evolution of irrigated RF ablation catheters enables the transfer of more power to the tissue and thereby increases the dimensions of the lesions. Cryoablation represents a valuable alternative. Cooling of tissue to -80 °C causes the intra- and extracellular formation of ice crystals, finally resulting in a dense circumscribed scar. The cryomapping procedure grants improved surveillance of the safety of ablation. Cryoenergy is very popular for pulmonary vein isolation (PVI) using the cryoballoon. In addition to the laser balloon that is established for PVI, ultrasound, microwaves, and stereotactic irradiation complete the arsenal.

Lumped Element Electrical Model based on Three Resistors for Electrical Impedance in Radiofrequency Cardiac Ablation: Estimations from Analytical Calculations and Clinical Data

The electrical impedance measured during radiofrequency cardiac ablation (RFCA) is widely used in clinical studies to predict the heating evolution and hence the success of the procedure. We hypothesized that a model based on three resistors in series can mimic the total electrical impedance measured during RFCA. The three resistors or impedances are given by: impedance associated with the tissue around the active electrode (myocardium and circulating blood) (Z-A), that associated with the tissue around the dispersive electrode (Z-DE) and that associated with the rest of the body (Z-B). Our objective was to quantify the values associated with these three impedance types by an analytical method, after which the values obtained would be compared to those estimated from clinical data from previous studies. The results suggest that an RFCA using a 7 Fr 4-mm electrode would give a Z-A of around 75 ohms, a Z-DE around 20 ohms, and Z-B would be 15±10 ohms (for body surface area variations between 1.5 and 2.5 m^2). Finally, adaptations of the proposed model were used to explain the results of previous clinical studies using a different electrode arrangement, such as in bipolar ablation of the ventricular septum.

Current role of atrioventricular junction (AVJ) ablation

Atrioventricular junction ablation with permanent pacemaker insertion is a highly effective treatment approach in patients with atrial fibrillation that is resistant to other treatment modalities, especially in the elderly or those with severe comorbidities. This effect likely reflects reversal of rapid ventricular rates and regularizing ventricular rates. There is increasing evidence that cardiac resynchronization therapy devices may be beneficial in selected populations after atrioventricular node ablation. The limitations of this approach include continued need for anticoagulation and lifelong pacemaker therapy.

How to avoid development of AV block during RF ablation: anatomical and electrophysiological analyses at the time of AV node ablation

BACKGROUND

With an aim to identify risk factors that can serve for prevention of atrioventricular (AV) block (AVB) during radiofrequency (RF) ablation, we conducted anatomical and electrophysiological investigations at the time of AV node ablation (AVNA).

METHODS AND RESULTS

Ten patients who underwent AVNA were enrolled. RF energy was delivered from posterior region of septal annulus of the tricuspid valve to the His bundle potential (HBP) recording site using a stepwise approach. In each delivery, atrial/ventricle potential amplitude ratio (A/V ratio), HBP, and juctional ectopy (JE) that appeared during RF delivery were evaluated. Furthermore, fluoroscopic distance between ablation site and HBP recording site (anatomical H-ABL distance) and electrophysiological H-ABL interval were measured. HBP was recorded in 25 of total 70 RF deliveries. When HBP was recorded, the A/V ratio was significantly greater in the group with AVB than without AVB (1.6 ± 2.3 mV vs 0.1 ± 0.2 mV, P = 0.02). The minimum cycle length (CL) of JE was significantly shorter in the group with AVB than without AVB (438 ± 112 ms vs 557 ± 178, ms, P = 0.04). AVB developed frequently when H-ABL distance was less than 15 mm from right anterior oblique view 30° and 12 mm from left anterior oblique view 45° and when H-ABL interval was less than 10 ms. AVB did not develop over the above values.

CONCLUSIONS

HBP with high A/V ratio, JE with short CL, short H-ABL distance, and short H-ABL interval of less than 10 ms should be avoided to prevent AVB during RF ablation at the near site of AV node.

Non-pharmacological, non-ablative approaches for the treatment of atrial fibrillation: experimental evidence and potential clinical implications

In this review, we initially covered the basic and clinical reports that provided the prevalent concepts underlying the mechanisms for atrial fibrillation (AF). The clinical evolution of catheter ablation and its eventual application to AF has also been detailed. A critique of the results based on a review of the literature has shown that either or both drugs or catheter ablation therapy for preventing AF recurrences have significant limitations and even serious complications. Finally, we have presented recent experimental studies which suggest that an alternative approach to reducing AF inducibility can be achieved with low-level autonomic nerve stimulation. Specifically, electrical stimulation of the vago-sympathetic trunks, at levels well below that which slows the heart rate can significantly increase AF thresholds and suppress AF inducibility. Further studies will determine if this new method can be used as an effective means of treating some forms of clinical AF.

Atrial fibrillation: a review of mechanism, etiology, and therapy

The prevalence of elderly individuals in the populations of developed countries is increasing rapidly, and atrial fibrillation (AF) is quite common in these elderly patients: currently, 11% of the U.S. population is between the ages of 65 and 85 years; 70% of people with AF are between the ages of 65 and 85 years. AF causes symptoms secondary to hemodynamic derangements that are the result of increased ventricular response and loss of atrial booster function. AF can lead to reversible impairment of left ventricular function, cardiac chamber dilatation, clinical heart failure, and thromboembolic events. AF requires treatment in order to prevent these potential complications. Type Ia, Ic, and III antiarrhythmics are capable of converting AF to normal sinus rhythm (NSR). Amiodarone has the greatest efficacy and safety for converting AF and maintaining NSR while digoxin and verapamil are ineffective in restoring NSR. Quinidine, flecainide, disopyramide, and sotalol have also been shown to maintain NSR after conversion of AF. Proarrhythmia is a definite concern with the latter four agents. Alternative therapy for AF includes anticoagulation with warfarin or aspirin for the prevention of thromboembolic events, and a variety of agents to control the ventricular response. All medications used to treat AF carry significant risks in the elderly, whether from proarrhythmia, overdosing because of compliance errors, or hemorrhage secondary to anticoagulation. Treatment of AF must be based on a careful risk-benefit evaluation. The physician must know the capability of the particular patient as well as drug mechanisms and effects in the elderly. The decision to convert patients from AF to NSR or to leave the patient in AF and control the ventricular response represents a complex intellectual challenge. Factors favoring one or the other of these two clinical strategies are discussed. Multicenter clinical trials, for example, the Atrial Fibrillation Follow-up Investigation Rhythm Management (AFFIRM) trial, are currently underway to assess various clinical strategies for maintenance of NSR following conversion from AF. Amiodarone is one of the drugs under investigation.

An approach to ablate and pace:AV junction ablation and pacemaker implantation performed concurrently from the same venous access site

BACKGROUND

Atrioventricular junction (AVJ) ablation combined with permanent pacemaker implantation (the "ablate and pace" approach) remains an acceptable alternative treatment strategy for symptomatic, drug-refractory atrial fibrillation (AF) with rapid ventricular response. This case series describes the feasibility and safety of catheter ablation of the AVJ via a superior vena caval approach performed during concurrent dual-chamber pacemaker implantation.

METHODS

A total of 17 consecutive patients with symptomatic, drug-refractory, paroxysmal AF underwent combined AVJ ablation and dual-chamber pacemaker implantation procedure using a left axillary venous approach. Two separate introducer sheaths were placed into the axillary vein. The first sheath was used for implantation of the pacemaker ventricular lead, which was then connected to the pulse generator. Subsequently, a standard ablation catheter was introduced through the second axillary venous sheath and used for radiofrequency (RF) ablation of the AVJ. After successful ablation, the catheter was withdrawn and the pacemaker atrial lead was advanced through that same sheath and implanted in the right atrium.

RESULTS

Catheter ablation of the AVJ was successfully achieved in all patients. The median number of RF applications required to achieve complete AV block was three (range 1-10). In one patient, AV conduction recovered within the first hour after completion of the procedure, and AVJ ablation was then performed using the conventional femoral venous approach. There were no procedural complications.

CONCLUSION

Catheter ablation of the AVJ can be performed successfully and safely via a superior vena caval approach in patients undergoing concurrent dual-chamber pacemaker implantation.

Preserved left ventricular ejection fraction following atrioventricular junction ablation and pacing for atrial fibrillation

INTRODUCTION

Right ventricular apical (RVA) pacing creates ventricular dyssynchrony and may compromise left ventricular ejection fraction (LVEF). The impact of RVA pacing in patients who have undergone atrioventricular junction (AVJ) ablation for atrial fibrillation (AF) is unclear. We sought to determine whether RVA pacing after AVJ ablation for patients with AF compromises LVEF in the short- or long-term.

METHODS/RESULTS

We studied 286 patients with AF who underwent AVJ ablation and RVA pacing at our institution between 1990 and 2002. Patients were stratified into a short-term follow-up group (LVEF reassessed by echocardiography within a year after AVJ ablation, n = 134) and a long-term group (LVEF reassessed after a year, n = 152). Among all 286 patients (mean follow-up 20 months), we observed no change in mean LVEF after AVJ ablation and RVA pacing (48% before vs. 48% after, P = 0.42). Short-term follow-up patients had a statistically significant improvement in mean LVEF (46% before vs. 49% after, P = 0.03), whereas there was no statistically significant change in mean LVEF in long-term follow-up patients (49% before vs. 48% after, P = 0.37). Only 9% of short-term patients, 15% of long-term patients, and 1% of patients with baseline LVEF <or= 40% experienced >or=10% absolute decrease in LVEF. Baseline LVEF > 40% was a multivariate predictor of LVEF decline.

CONCLUSIONS

RVA pacing after AVJ ablation does not compromise LVEF in the short- or long-term for the vast majority of patients. Better predictors are needed to help us select patients for biventricular pacing after AVJ ablation.

Regular supraventricular tachycardias associated with idiopathic atrial fibrillation

The present study analyzed the recurrence rate of idiopathic atrial fibrillation (AF) after elimination by radiofrequency ablation of the substrate for a regular tachycardia. Forty consecutive patients with idiopathic AF and a history of regular palpitations or documented regular tachyarrhythmias were prospectively included. Regular tachyarrhythmias were induced in 82.5% of patients: atrial flutter (42.4% of the inducible arrhythmias), atrial tachycardia (24.2%), atrioventricular (AV) nodal reentry (18.2%), AV reentry through a concealed accessory pathway (9.1%), and AV nodal reentry associated with right atrial tachycardia (6.1%). Dual AV node physiology with single or dual AV node echoes was demonstrated in 6.1% of patients without inducible arrhythmias. During follow-up (92 +/- 11 months), AF recurred in 19.2% of patients after successful radiofrequency ablation and in 69.2% after unsuccessful or not performed procedures (p <0.05). Left atrial diameter did not change after successful ablation but increased significantly in the population without elimination of the substrate (initial diameter 37.5 +/- 2 mm, final diameter 46.4 +/- 3.2 mm; p <0.05). In conclusion, the systematic search for the substrate of regular tachyarrhythmias followed by their elimination by catheter ablation reduces the recurrence of idiopathic AF in patients with a history of regular palpitations or documented regular tachyarrhythmias.

Electrophysiological Characteristics of Junctional Rhythm During Ablation of the Slow Pathway in Different Types of Atrioventricular Nodal Reentrant Tachycardia

BACKGROUND

Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined.

METHODS

Forty-five patients who underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia were included; 27 patients with slow-fast, 11 patients with slow-intermediate, and 7 patients with fast-slow AV nodal reentrant tachycardia. The atrial activation pattern and HA interval (from the His-bundle potential to the atrial recording of the high right atrial catheter) during AV nodal reentrant tachycardia (HA(SVT)) and JR (HA(JR)) were analyzed.

RESULTS

In all patients with slow-fast AV nodal reentrant tachycardia, the atrial activation sequence recorded during JR was similar to that of the retrograde fast pathway, and transient retrograde conduction block during JR was found in 1 (4%) patient. The HA(JR) was significantly shorter than the HA(SVT) (57 +/- 24 vs 68 +/- 21 ms, P < 0.01). In patients with slow-intermediate AV nodal reentrant tachycardia, the atrial activation sequence of the JR was similar to that of the retrograde fast pathway in 5 (45%), and to that of the retrograde intermediate pathway in 6 (55%) patients. Transient retrograde conduction block during JR was noted in 1 (9%) patient. The HA(JR) was also significantly shorter than the HA(SVT) (145 +/- 27 vs 168 +/- 29 ms, P = 0.014). In patients with fast-slow AV nodal reentrant tachycardia, retrograde conduction with block during JR was noted in 7 (100%) patients. The incidence of retrograde conduction block during JR was higher in fast-slow AV nodal reentrant tachycardia than slow-fast (7/7 vs 1/11, P < 0.01) and slow-intermediate AV nodal reentrant tachycardia (7/7 vs 1/27, P < 0.01).

CONCLUSIONS

In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.

Clinical results with catheter ablation: AV junction, atrial fibrillation and ventricular tachycardia

With the limitations of pharmacologic and device therapies for atrial fibrillation and ventricular tachycardia, catheter ablation is assuming a larger role in the management of patients with these common arrhythmias. Multiple case series and clinical trials have helped to define the evolving role of these techniques for ablation of the atrioventricular node, atrial fibrillation, and ischemic ventricular tachycardia. Based on very low complication rates, excellent efficacy and proven outcomes with radiofrequency ablation of the atrioventricular node, this approach with permanent pacing should play a larger role in the treatment of symptomatic patients with permanent atrial fibrillation. While linear ablation of atrial fibrillation has limited clinical utility for the treatment of this common arrhythmia, the results of multiple case series of focal atrial fibrillation ablation indicate the potential for an expanding role of this curative technique. Catheter ablation techniques for ventricular tachycardia in the setting of coronary artery disease have a role as supplemental therapy to the implantable cardioverter defibrillator in patients with recurrent pharmacologically refractory ventricular arrhythmias requiring frequent device interventions.

High incidence of thrombus formation without impedance rise during radiofrequency ablation using electrode temperature control

The authors hypothesized that during RF ablation, the electrode to tissue interface temperature may significantly exceed electrode temperature in the presence of cooling blood flow and produce thrombus. In 12 anesthetized dogs, the skin over the thigh muscle was incised and raised to form a cradle that was superfused with heparinized canine blood (ACT > 350 s) at 37 degrees C. A 7 Fr, 4-mm or 8-mm ablation electrode containing a thermocouple was held perpendicular to the thigh muscle at 10-g contact weight. Interface temperature was measured at opposite sides of the electrode using tiny optical probes. RF applications (n = 157) were delivered at an electrode temperature of 45 degrees C, 55 degrees C, 65 degrees C, and 75 degrees C for 60 seconds, with or without pulsatile blood flow (150 mL/min). Without blood flow, the interface temperature was similar to the electrode temperature. With blood flow, the interface temperature (side opposite blood flow) was up to 36 degrees C and 57 degrees C higher than the electrode temperature using the 4- and 8-mm electrodes, respectively. After each RF, the cradle was emptied and the electrode and interface were examined. Thrombus developed without impedance rise at an interface temperature as low as 73 degrees C without blood flow and 80 degrees C with blood flow (11/16 RFs at 65 degrees C electrode temperature using 4 mm and 13/13 RFs at an electrode temperature of 55 degrees C using an 8-mm electrode with blood flow). With blood flow, interface temperature markedly exceeded the electrode temperature and the difference was greater with an 8-mm electrode (due to greater electrode cooling). In the presence of blood flow, thrombus occurred without an impedance rise at an electrode temperature as low as 65 degrees C with a 4-mm electrode and 55 degrees C with an 8-mm electrode.

Selective atrionodal input ablation for induction of proximal complete heart block with stable junctional escape rhythm in patients with uncontrolled atrial fibrillation

BACKGROUND

The study tests the hypothesis that ablating all inputs to the atrioventricular (AV) node can result in complete heart block with stable junctional escape rhythm.

METHODS AND RESULTS

We attempted atrionodal input ablation in 76 consecutive patients with uncontrolled atrial fibrillation. Fast and slow pathways were first ablated. If there was no AV block, additional energy applications were done between fast and slow pathway locations. The patients were followed for 42 +/- 11 months. Group I (n = 57) comprised patients with complete heart block and junctional escape rhythm (53 +/- 4 beats/min) at the end of the procedure. The escape rhythm remained stable throughout follow-up. Group II (n = 15) were patients who failed the stepwise atrionodal input ablation and required AV junctional ablation guided by His bundle potential to achieve complete heart block. Four patients showed a slow escape rhythm after ablation (33 +/- 4 beats/min). Others had no escape rhythm. All 15 pts remained pacemaker dependent. The total death rate of groups I and II was 18/57 (31.6%) vs 10/15 (66.7%), respectively (p < 0.02). These differences could not be explained by a difference of left ventricular ejection fraction (0.42 +/- 0.07 vs 0.41 +/- 0.04, respectively, p = NS).

CONCLUSIONS

(1) In most patients, ablation of both fast and slow pathways did not result in complete heart block, indicating the presence of multiple atrionodal inputs. (2) Ablation of all atrionodal inputs may result in complete heart block with stable junctional escape rhythm. (3) As compared with AV junctional ablation, atrionodal input ablation was associated with a lower mortality rate on long-term follow up.

Atrial fibrillation in patients with heart failure

Atrial fibrillation and heart failure are very common cardiac disorders, and both are associated with symptoms, significant morbidity, and mortality. Studies have attempted to determine the prognostic significance of atrial fibrillation in patients with heart failure. Whether atrial fibrillation is an independent risk factor of mortality remains controversial. Multiple trials using either pharmacologic or nonpharmacologic therapies in an attempt to manage atrial fibrillation have been developed. The purposes of this review are to present an overview of atrial fibrillation in patients with heart failure and to discuss the prevalence, prognostic significance, complications, mechanisms, and trials that have formed the therapies presently used.

Maintaining stability of sinus rhythm in atrial fibrillation: antiarrhythmic drugs versus ablation

In managing atrial fibrillation, the main therapeutic strategies include rate control, termination of the arrhythmia, and pr vention of recurrences and thromboembolic events. Rate control with digoxin, b-blockers, verapamil, and diltiazem may be preferred in drug refractory and sedentary patients with markedly dilated left atrium and atrial fibrillation of long duration. Drugs useful in the maintenance of sinus rhythm include quinidine, procainamide, disopyramide, sotalol, amiodarone, dofetilide, flecainide, and propafenone. In patients with structural heart disease, the class III antiarrhythmics are the initial drugs of choice, given their neutral effects on survival in a post-myocardial infarction and congestive heart failure population. Due to high recurrence rates with pharmacologic therapy, nonpharmacologic options of therapy include atrioventricular junction ablation, atrial defibrillators, catheter ablation of pulmonary vein foci, and attempts to perform an atrial Maze procedure using catheters. Hybrid therapy using drugs in combination with nonpharmacologic approaches will be used more frequently in the future for refractory patients.

Sudden death after radiofrequency ablation of the atrioventricular node in patients with atrial fibrillation

OBJECTIVES

We evaluated the incidence and predictors of sudden death after atrioventricular (AV) node ablation and pacemaker implantation.

BACKGROUND

Sudden death may occur after radiofrequency catheter ablation of the AV node and pacemaker implantation in patients with atrial fibrillation (AF). Whether it is related to the procedure or to pre-existing heart disease remains unclear.

METHODS

All patients who had radiofrequency catheter ablation of the AV node and pacemaker implantation for rate control of medically refractory AF were identified retrospectively and observed prospectively. All patients with sudden death after ablation were identified. The relationship between the procedure and sudden death was defined on the basis of the time between the two as "likely," "possibly" or "unlikely."

RESULTS

Of 334 consecutive patients with AF who underwent AV node ablation, nine had sudden death after the ablation. Four patients (1.2%) had sudden death likely related to the procedure: in 3 patients, arrest occurred within 48 h after the procedure; in one patient, arrest occurred four days after the procedure. In three other patients (0.9%), sudden death was possibly related to the procedure because the event occurred within three months afterward. The remaining two deaths were unrelated to the procedure. Diabetes, New York Heart Association functional class (>or=II), preprocedure ventricular arrhythmia, mitral or aortic stenosis, aortic regurgitation and chronic obstructive pulmonary disease were independent predictors for sudden death.

CONCLUSIONS

Sudden death likely or possibly related to catheter ablation occurred in 7 of 334 patients (2.1%). Risk of sudden death is highest within two days after the procedure.

Atrial pacing during radiofrequency ablation of junctional ectopic tachycardia--a useful technique for avoiding atrioventricular bloc

Radiofrequency catheter ablation (RFCA) was performed on a 5-year-old boy with congenital junctional ectopic tachycardia (JET) that was refractory to medical management. Because of the lack of retrograde atrial depolarization during tachycardia, radiofrequency energy was delivered during atrial overdrive pacing to confirm the presence of preserved atrioventricular (AV) conduction. Although the procedure was complicated by complete right bundle branch block after ablation of the para-Hissian region, the patient regained sinus rhythm accompanied by normal AV conduction. Rapid atrial pacing during RFCA of JET may be safely used to avoid AV block.

Comparison of effectiveness of an 8-mm versus a 4-mm tip electrode catheter for radiofrequency ablation of typical atrial flutter

An 8-mm catheter does not appear superior to 4-mm tip electrode for atrial flutter ablation. The potential advantage of allowing higher energy delivery on a larger surface is compensated by the lack of consistent contact with the endocardial surface.

Parahisian radiofrequency catheter ablation in dogs: comparison of the above-valve and below-valve approaches

In patients with an accessory pathway close to the His bundle, radiofrequency catheter ablation (RFCA) requires additional care to avoid damage to the normal conduction system. To assess differences between approaches from above or below the tricuspid valve (TV), we performed RFCA in 20 dogs (from above, group A, n=10; from below, group B, n=10). RF energy with temperature control at 60 degrees 60 seconds was administered at the site where a small His potential was recorded from the ablation catheter guided by fluoroscopy and transesophageal echocardiography (TEE) (in the latter six dogs). Before and after RFCA, electrophysiological testing was performed and histological findings were compared. An ablated lesion was created in 7 of 10 (2 of 2 guided by TEE) dogs in group A and 5 of 10 (3 of 4 TEE) dogs in group B. In group A, an ablated lesion involved the atrium and ventricle in the anterior site of His bundle, but the lesion was only in the ventricle in group B. An atrioventricular block (AVB) and severe damage to the penetrating bundle was observed in one dog of group A. A large hematoma on the TV was made in 2 dogs and the complete right bundle branch block (CRBBB) occurred in 3 dogs of group B. The approach from below the TV was safer than that from above the TV in parahisian RFCA, because it did not create an AVB, although it has a high incidence of CRBBB and associated technical difficulties.

A low amplitude His-bundle potential predicts failure of the right-sided approach for atrioventricular junction ablation

In 30 patients with drug refractory atrial fibrillation-flutter who underwent radiofrequency (RF) ablation of the atrioventricular (AV) junction, 23 were successfully ablated using the conventional right-sided approach (group A). Seven patients required a left-sided approach (group B) after multiple applications from the conventional right-sided approach failed to produce complete AV block. The amplitude of the His-bundle potential recorded at the ablation site differed significantly between the 2 groups (0.23+/-0.11 mV in group A vs 0.12+/-0.04 mV in group B; p<0.005). Also, the amplitude of the His-bundle potential recorded in the standard position across the tricuspid annulus differed significantly between the 2 groups (0.27+/-0.35 mV in group A vs 0.11+/-0.44 mV in group B; p<0.007). There was no significant difference in the amplitude of the ventricular potential between the 2 groups. The probability of successful ablation of the AV junction with a conventional right-sided approach was 6 out of 12 patients (50%) if the His amplitude was <0.12mV, and 17 out of 18 patients (94%) if the His amplitude was >0.12mV (p<0.005). Patients in group B had a mean of 20.5+/-13.0 failed right-sided RF applications (5-33 applications), but required a mean of only 2 subsequent RF applications for success on the left side (1-6 applications). The His-amplitude recorded from the left side using the same catheter was significantly greater than that on the corresponding right-side (0.22+/-0.09 mV on the left side vs 0.12+/-0.04 mV on the right side: p<0.05). Total mean fluoroscopic time was 62+/-12min for group B and 20+/-13min for group A patients. In patients that underwent RF ablation of the AV junction, a maximum His amplitude <0.12 mV predicted a success rate of approximately 50% in the present study. An early switch to a left-sided approach may avoid multiple RF applications and prolonged fluoroscopic time in patients with a low amplitude His-bundle potential.

Prevalence and characteristics of escape rhythms after radiofrequency ablation of the atrioventricular junction: results from the registry for AV junction ablation and pacing in atrial fibrillation. Ablate and Pace Trial Investigators

BACKGROUND

Radiofrequency ablation of the atrioventricular junction is a well-established procedure for the management of atrial fibrillation refractory to medical therapy. However, there are few data available on the prevalence and characteristics of the escape rhythms that are present after the procedure.

METHODS

The Ablate and Pace Trial was a prospective, multicenter registry of atrioventricular junction ablation and pacing in atrial fibrillation. Ablation of the atrioventricular junction was accomplished with radiofrequency energy with standard techniques. Before discharge from the hospital, patients underwent a systematic analysis of the rate and morphologic features of the escape rhythm, if any, that was present when the pacing rate was gradually decreased.

RESULTS

There were 156 patients from 16 centers who underwent attempted radiofrequency ablation of the atrioventricular junction. The procedure was successful in 155 (99%) of 156 patients. An escape rhythm was present in 104 patients (67%) after radiofrequency ablation. The escape rate ranged from 11 to 65 beats/min (mean 39 +/- 10 beats/min). Only 49 patients (31%) had an escape rate >/=40 beats/min. Of the 104 patients with an escape rhythm, 53 patients (51%) had a QRS that was unchanged from baseline. There was no correlation between the number of radiofrequency applications and the presence of an escape rhythm.

CONCLUSION

The majority of patients who undergo radiofrequency catheter ablation of the atrioventricular junction are pacemaker dependent after the procedure, as defined by lack of an escape rhythm or the presence of an escape rhythm that is <40 beats/min.

Mitral regurgitation after atrioventricular node catheter ablation for atrial fibrillation and heart failure: acute hemodynamic features

BACKGROUND

Radiofrequency catheter ablation of the atrioventricular node and pacemaker insertion have been associated with occasional development of mitral regurgitation (MR). Ventricular pacing might result in MR if (1) left ventricular (LV) compliance is decreased and/or (2) mitral valve leaflet apposition is disturbed. We studied acute hemodynamic changes resulting from initiation of ventricular pacing in patients undergoing ablation.

METHODS AND RESULTS

Thirteen patients (10 men and 3 women) with a mean age of 73.4 +/- 8. 6 years, with chronic atrial fibrillation and congestive heart failure, had permanent ventricular pacemaker insertion with lead placement at the right ventricular (RV) apex. The following hemodynamic recordings were obtained before ablation (during atrial fibrillation) and then immediately after ablation (during RV pacing): heart rate, mean arterial pressure, LV end-diastolic pressure (LVEDP), mean pulmonary capillary wedge pressure, V-wave amplitude, and cardiac index. Presence of MR was assessed by V-wave amplitude and the results of LV angiography. In patients who had MR, recordings were also obtained during temporary ventricular pacing from the RV outflow tract (RVOT). As a group there were no significant changes in any hemodynamic measurement. Before ablation, mild MR by LV angiogram was present in 5 patients, but none had large V-wave amplitude. After ablation, mild MR was present by LV angiogram in 6 patients, and in 3 of these patients large V-wave amplitude developed (mean amplitude 42.7 +/- 2.2 mm Hg; assigned to group 1). This was associated with a rise in LVEDP in 1 patient (consistent with reduced LV compliance), but LVEDP was unchanged in the other 2 patients (suggesting abnormal mitral valve leaflet apposition). All patients in group 1 exhibited a fall in V-wave amplitude when the pacing site was moved to the RVOT.

CONCLUSIONS

Both reduced LV compliance and disturbed mitral valve leaflet apposition contribute to MR after ablation. MR is reduced by pacing from the RVOT.

Thromboembolism after atrioventricular node ablation and pacing: long term follow up

OBJECTIVE

To assess the incidence of arterial embolic events in patients with high rate, drug resistant, severely symptomatic paroxysmal and chronic atrial fibrillation who have undergone atrioventricular (AV) node ablation and permanent pacing.

DESIGN

Multicentre retrospective cohort study. PATIENTS AND MANAGEMENT: From May 1987 to January 1997, AV node ablation was performed in 585 severely symptomatic patients (mean (SD) age 66 (11) years) with high rate, drug resistant paroxysmal atrial fibrillation (308) or chronic atrial fibrillation (277). Lone atrial fibrillation was present in 133 patients, while the remaining 452 suffered from dilated, ischaemic, or valvar heart disease. Patients underwent VVIR (454) or DDDR (131) pacemaker implantation, after AV node ablation. Antiplatelet agents were given to 202 patients, warfarin to 187 patients.

RESULTS

During a follow up of 33.6 (24.2) months, thromboembolic events were observed in 17 patients (3%); the actuarial occurrence rates of thromboembolism were 1.1%, 3%, 4.2%, and 7.4% after one, three, five, and seven years, respectively. Among five variables, univariate analysis showed that only the presence of chronic atrial fibrillation at the time of ablation (relative risk (RR) = 1.8, 95% confidence interval (CI) = 1.02 to 3. 20, p = 0.04) and the need for warfarin treatment (RR = 1.6, 95% CI 1.00 to 2.71, p = 0.048) were associated with a significantly higher risk of occurrence of thromboembolic events. On multivariate analysis the only predictor of embolic events during the follow up was the presence of chronic atrial fibrillation.

CONCLUSIONS

Data from this large cohort of patients indicate a fairly low incidence (1.04% per year) of thromboembolic events after AV node ablation and pacing for drug refractory, high rate atrial fibrillation.

Radiofrequency ablation of atrioventricular junction and pacemaker implantation versus modulation of atrioventricular conduction in drug refractory atrial fibrillation

Modulation of atrioventricular (AV) node conduction and radiofrequency ablation of AV junction are alternative approaches to control ventricular rate in drug refractory atrial fibrillation (AF). In 2 centers, 120 patients were treated either with AV junction ablation (center 1, group 1, 60 patients [30 men, aged 64 +/- 11 years], paroxysmal AF in 24 patients) or with modulation (group 2, 60 patients [32 men, aged 58 +/- 12 years], paroxysmal AF in 43 patients). In group 1, complete AV block was achieved in all patients. In group 2, the procedure was performed in sinus rhythm (30 patients), prolonging the Wenckebach cycle length from 328 +/- 85 to 466 +/- 80 ms (p <0.01) or during AF (30 patients), decreasing ventricular rate from 178 +/- 35 to 96 +/- 35 beats/min (p <0.01), and to <100 beats/min in 17 patients (61%). Complete AV block was induced in 9 of 60 patients (15%). In groups 1 and 2, at a follow-up of 27 +/- 7 and 26 +/- 6 months, there were 2 deaths (1 cardiac, 1 sudden death) and 1 death for end-stage heart failure, respectively. Hospital readmissions decreased from 3.2 to 0.2 and from 4.2 to 0.2/year; late AF recurrences at of >120 beats/min were documented in 6% and 12%, respectively. Symptom score analysis including effort and rest dyspnea, exercise intolerance, weakness, and palpitation showed a significant improvement in both treatment groups, when acutely effective, in patients with paroxysmal and/or chronic AF. In conclusion, ablation of the AV junction shows a higher acute success rate compared with modulation of the AV node conduction in patients with drug refractory AF. Depending on the acute success, both approaches therefore were similarly effective in achieving long-term ventricular rate control and symptom score improvement.

Atrial ectopy originating from the posteroinferior atrium during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia

Atrial ectopy sometimes appears during RF ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examine these issues, we analyzed 67 consecutive patients with AVNRT (60 with slow-fast AVNRT and 7 with fast-slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patients. During successful RF ablation, junctional ectopy with the activation sequence showing H-A-V at the His-bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A-H-V at the His-bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 patients) or without junctional ectopy (5 patients). Before RF ablation, retrograde slow pathway conduction induced during ventricular burst and/or extrastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.001). Successful ablation site in group A was distributed between the His-bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coronary sinus ostium. In group B, atrial ectopy also appeared in 21% of the unsuccessful RF ablations. In conclusion, atrial ectopy is relatively common during slow pathway ablation and observed in 8% of RF applications overall and 22% of RF applications that successfully eliminated inducible AVNRT. Atrial ectopy appears to be closely related to successful slow pathway ablation among patients with manifest retrograde slow pathway function.

Defibrillation-guided radiofrequency ablation of atrial fibrillation secondary to an atrial focus

OBJECTIVES

Our aim was to evaluate a potential focal source of atrial fibrillation (AF) by unmasking spontaneous early reinitiation of AF after transvenous atrial defibrillation (TADF), and to describe a method of using repeated TADF to map and ablate the focus.

BACKGROUND

Atrial fibrillation may develop secondary to a rapidly discharging atrial focus that the atria cannot follow synchronously, with suppression of the focus once AF establishes. Focus mapping and radiofrequency (RF) ablation may be curative but is limited if the patient is in AF or if the focus is quiescent. Early reinitiation of AF has been observed following defibrillation, which might have a focal mechanism.

METHODS

We performed TADF in patients with drug-refractory lone AF using electrodes in the right atrium (RA) and the coronary sinus. When reproducible early reinitiation of AF within 2 min after TADF was observed that exhibited a potential focal mechanism, both mapping and RF ablation were performed to suppress AF reinitiation. Clinical and ambulatory ECG monitoring was used to assess AF recurrence.

RESULTS

A total of 44 lone AF patients (40 men, 4 women; 32 persistent, 12 paroxysmal AF) with a mean age of 58+/-13 years underwent TADF. Sixteen patients had early reinitiation of AF after TADF, nine (20%; 5 paroxysmal) exhibited a pattern of focal reinitiation. Earliest atrial activation was mapped to the right superior (n = 4) and the left superior (n = 3) pulmonary vein, just inside the orifice, in the seven patients who underwent further study. At the onset of AF reinitiation, the site of earliest activation was 86+/-38 ms ahead of the RA reference electrogram. The atrial activities from this site were fragmented and exhibited progressive cycle-length shortening with decremental conduction to the rest of the atrium until AF reinitiated. Radiofrequency ablation at the earliest activation site resulted in suppression of AF reinitiation despite pace-inducibility. Improved clinical outcome was observed over 8+/-4 months' follow-up.

CONCLUSIONS

Transvenous atrial defibrillation can help to unmask, map, and ablate a potential atrial focus in patients with paroxysmal and persistent AF. A consistent atrial focus is the cause of early reinitiation of AF in 20% of patients with lone AF, and these patients may benefit from this technique.

Reduction of atrial fibrillation inducibility by radiofrequency ablation: an experimental study

A study is made of the antifibrillatory effects of radiofrequency (RF)-induced atrial lesions using nine Langendorff-perfused rabbit hearts in which the atrial electrophysiological properties and atrial fibrillation (AF) inducibility were modified by atrial stretching. Using a multiple electrode consisting of 121 unipolar electrodes, determinations were made of the atrial refractory periods, conduction velocity, wavelength of the atrial activation process, and the inducibility of sustained AF episodes (duration over 30 s) by atrial burst pacing in four situations: (a) control; (b) following dilatation of the right atrium; (c) after adding an RF linear lesion at the cava-tricuspid annulus isthmus; and (d) after adding two RF linear lesions rounding the base of the right atrial appendage and extending from the inferior zone of the sulcus terminalis to the anterior wall of the appendage. Under control conditions, AF was not induced in any of the experiments. The wavelengths were 10.5 +/- 1.2 cm for basic cycles of 250 ms and 6.6 +/- 0.5 cm for cycles of 100 ms. Following dilatation, a significant decrease was recorded in the atrial refractory periods, conduction velocity, and wavelength, which reached values of 6.1 +/- 0.7 cm (250-ms cycle, P < 0.01), and 3.9 +/- 0.3 cm (100-ms cycle, P < 0.01); AF was induced in five cases (P < 0.05). After producing the lesion at the cava-tricuspid isthmus, the electrophysiological modifications induced by atrial dilatation persisted (wavelength = 6.2 +/- 0.6 cm (250-ms cycle) and 4.3 +/- 0.3 cm (100-ms cycle); P < 0.01 vs the control) and AF was triggered in eight cases (P < 0.0001). In turn, on adding the two lesions at the right atrial free wall and appendage, AF was induced only in one experiment (P = NS vs control), and the dilatation-induced decrease in refractoriness and wavelength was attenuated. Nevertheless, differences remained significant with respect to the controls, with the exception of the functional refractory periods determined at cycles of 100 ms. In this phase, the wavelength was 6.6 +/- 0.7 cm (250-ms cycle, P < 0.01 vs control) and 4.9 +/- 0.5 cm (100-ms cycle; P < 0.05). Atrial conduction between the zones separated by the lesions was blocked at any frequency, or selectively at rapid atrial activation frequencies.

IN CONCLUSION

(a) the production of three linear lesions in the right atrium (cava-tricuspid isthmus, atrial appendage, and inferior free wall) reduces AF inducibility in the experimental model used; (b) conduction block (either absolute or frequency dependent) through the lesions, reduction in tissue mass caused by lesion creation, and possibly the attenuation of the shortening of atrial refractoriness and wavelength in the zones not separated by the lesions are implicated in the reduction of AF inducibility; and (c) the single lesion in the cava-tricuspid isthmus does not impede AF inducibility.

Modulation of the atrioventricular node conduction to achieve rate control in patients with atrial fibrillation: long-term results

Modulation of the AV node reduces the ventricular rate during AF, without affecting AV conduction during sinus rhythm. Acute and long-term results of AV node modulation in 75 patients with AF and severe related symptoms of heart failure are presented in this study. The procedure involved, in all cases, the selective ablation of the posterior inputs to the AV node; in a subgroup of 15 patients with poor modification of AV conduction properties, a sequential approach involving subsequent anterior input ablation was performed. The procedure caused acutely a prolongation of the Wenckebach cycle length (38 patients in sinus rhythm) from 334 +/- 88 to 470 +/- 80 ms (P < 0.01), and a reduction of the average ventricular rate (37 patients in AF) from 154 +/- 31 to 88 +/- 40 beats/min (P < 0.01); permanent complete AV block was induced in 9 of 75 patients (12%). Considering the "sequential" approach, an increase of the Wenckebach cycle length from 362 +/- 50 to 530 +/- 45 ms (P < 0.01) and a reduction of the average heart rate in patients with AF from 158 +/- 16 to 81 +/- 20 beats/min (P < 0.01) was obtained in this subgroup of patients, in whom the AH interval prolonged from 93 +/- 12 to 175 +/- 27 ms, and no complete AV block was observed. At a mean follow-up of 23 +/- 9 months (range 2-48), the mean number of hospital admissions per patient per year decreased from 4.2 to 0.2. Five of 49 patients with paroxysmal AF and 3 of 26 patients with chronic AF had high rate recurrences (1 > 120 beats/min) that caused severe palpitations; these patients were considered as late clinical failures (8/75; 11%). All patients reported a substantial subjective improvement and an increased exercise tolerance, as documented by a semiquantitative questionnaire. There were no episodes of late AV block or sudden cardiac deaths. In conclusion, modulation of the AV node--either by slow pathway ablation, or by a "sequential" posterior and anterior approach in refractory patients--allows a long-term control of the ventricular rate and prevents the recurrence of severe clinical symptoms in more than 75% of patients with drug refractory AF.

Report of a study group on ablate and pace therapy for paroxysmal atrial fibrillation. Barcelona Discussion Group. Working Group on Arrhythmias of the European Society of Cardiology

Atrioventricular junctional (AVJ) catheter ablation followed by pacemaker implantation is now widely accepted for patients affected by paroxysmal atrial fibrillation (PAF) not controlled by antiarrhythmic drugs. However, few data exist on its indications, optimal methodology and complications. Therefore a study group examined current practice in Europe and North America, using a questionnaire, followed by a Study Group Meeting to discuss the results. Based upon this, class I, class II and class III indications were proposed. Class I indications (for which general agreement existed) include drug-refractory PAF, correlating with important symptoms, the bradycardia tachycardia syndrome already treated with a pacemaker, and continued PAF. Large differences exist in the current methodology, but consensus was reached on the technical approaches of right and left-sided AVJ ablation, and on the timing of pacemaker implant in relation to ablation. No complete agreement was reached on technical features such as catheter choice and heparin use. The recommended pacing mode was DDDR with mode switching.

Junctional tachycardia during radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia: effects of autonomic blockade

INTRODUCTION

The autonomic nervous system richly innervates the peri-AV nodal region and may be activated during radiofrequency (RF) ablation for AV nodal reentrant tachycardia, resulting in the generation of junctional tachycardia. The purpose of this prospective study was to determine the role of the autonomic nervous system in the genesis of junctional tachycardia.

METHODS AND RESULTS

We compared the characteristics of junctional tachycardia in patients with (n = 10) and without (n = 10) autonomic blockade undergoing RF ablation for AV nodal reentrant tachycardia. Intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg) were used to block the autonomic nervous system. There were no differences in clinical variables and baseline electrophysiologic characteristics between the two groups except for slightly longer effective refractory periods of the fast pathway and of the atrium in the autonomic blockade group. The autonomic blockade shortened the baseline sinus cycle length and effective refractory period of the ventricle only but not other electrophysiologic characteristics of the AV node. The junctional tachycardia was observed during ablation in each patient, but its occurrence and cycle length, as well as numbers of consecutive junctional beats, were not altered by the autonomic blockade.

CONCLUSION

Our results indicate that the muscarinic and beta-adrenergic components of the autonomic nervous system play no role in the genesis of junctional tachycardia.

Randomized comparison of slow pathway modification within the posteroseptal versus the midseptal area in patients with atrioventricular nodal reentrant tachycardia

A total of 332 local electrogram recordings including 62 successful and 270 unsuccessful sites were analyzed. Univariate analysis revealed that there was a longer duration and more peaks of the atrial electrogram with a lower atrioventricular ratio and a higher incidence and shorter onset time of junctional ectopy during energy delivery at successful than at unsuccessful target sites.

Effect of catheter tip length and position on lesion volume in temperature controlled RF ablation in canine tricuspid valve annulus

BACKGROUND

Radiofrequency (RF) energy has been delivered to the tricuspid valve annulus (TVA) in humans with both 4 mm and 8 mm long catheter tip electrodes to treat atrial flutter. However, lesion volume with temperature controlled RF delivery systems has not been previously characterized.

METHODS

In 10 anesthetized canines, a single pulse of temperature controlled RF energy at a 70 degrees C set point, 30 second duration was delivered with either a 7 Fr/4 mm tip or a 7 Fr/8 mm tip electrode in a position both anterolateral and posteroseptal to the tricuspid valve annulus (TVA). Surface echocardiogram was obtained prior and after ablation. The animals were sacrificed after ablation and the lesions underwent gross and histological examination.

RESULTS

Lesion size, tip temperature and power were related to tip electrode surface area (SA). Eight mm tips (SA = 59 mm2) tended to create significantly larger lesions than 4 mm tips (SA = 29 mm2). Median lesion volume was 22 vs. 1.5 mm3, respectively. Eight mm tips were also associated with higher power requirements and lower temperatures than 4 mm tips. Posteroseptal TVA lesions tended to be larger than anterolateral lesions. No significant complications were noted.

CONCLUSIONS

Using temperature controlled RF ablation, large lesions may be safely created on the canine TVA using 7 Fr catheters with 8 mm long tips.

The Ablate and Pace Trial: a prospective study of catheter ablation of the AV conduction system and permanent pacemaker implantation for treatment of atrial fibrillation. APT Investigators

BACKGROUND

The Ablate and Pace Trial (APT) prospectively assessed the effects of catheter ablation of the AV conduction system and permanent pacemaker implantation on health-related quality of life, survival, exercise capacity, and ventricular function in 156 patients with symptomatic atrial fibrillation.

METHODS

All patients referred for catheter ablation and permanent pacemaker implantation because of medically-refractory atrial fibrillation at 16 centers were screened for enrollment in a prospective registry. Baseline assessment prior to ablation included measurement of quality of life, including the Health Status Questionnaire, the Quality of Life Index and the Symptom Checklist: Frequency and Severity. Exercise capacity was assessed with metabolic treadmill exercise testing and ventricular function was quantitated with echocardiography. The quality of life instruments, exercise capacity, and echocardiography were repeated at 3 and 12 months after catheter ablation.

RESULTS

The APT population included 90 men and 66 women (66.1 +/- 11.5 years of age) with either chronic (n = 70), recurrent (n = 31), or paroxysmal atrial fibrillation (n = 55). Structural heart disease was present in 78.2% of patients. Successful ablation of AV conduction was achieved in 155 of 156 patients (99.4%). Survival at 1 year was 85.3%, with 5 of 23 deaths being sudden cardiac deaths. Survival over the first year of follow-up was significantly lower for patients with a baseline left ventricular ejection fraction (LVEF) < 0.45 (0.73) than for patients with a LVEF > or = 0.45 (0.88, p = 0.03). The NYHA functional class improved from 2.1 at baseline to 1.8 at 3 months and 1.9 at 12 months of followup (p = 0.0001). Significant improvement in quality of life scores were noted for all 8 subscales of the Health Status Questionnaire, for the overall rating of the Quality of Life Index, the Health and Function subscales; Arrhythmia-related symptoms were markedly reduced as measured by the Symptom Checklist: Frequency and Severity scale. The mean LVEF improved from 0.50 +/- 0.20 at baseline to 0.54 +/- 0.20 at 3 months (p = 0.03). The LVEF 12 months after ablation was 0.52 +/- 0.20, not statistically different from baseline. Individuals with reduced systolic function at baseline had the greatest improvement, from LVEF 0.31 +/- 0.20 at baseline to 0.41 +/- 0.20 at 3 months and 0.41 +/- 0.30 at 12 months (p = 0.0001). There were no significant changes in treadmill exercise duration (10.0 +/- 4.3 min at baseline and 11.6 +/- 3.6 min at 12 months) or VO2max (1467 +/- 681 ml O2 min baseline and 1629 +/- 739 ml O2 min at 12 months).

CONCLUSIONS

Catheter ablation of the AV conduction system and permanent pacemaker implantation were associated with improved quality of life and left ventricular function in this population of highly symptomatic patients with atrial fibrillation refractory to medical therapy.

Physiology of the escape rhythm after radiofrequency atrioventricular junctional ablation

The physiology of the escape rhythm (ER) and its response to pharmacological modulation under varying autonomic conditions were studied 48 patients undergoing radiofrequency ablation of the atrioventricular junction (AVJ) for refractory atrial fibrillation. The QRS morphology and cycle length (CL) of the baseline ER were measured 15 minutes postablation. The CL of the ER was measured in response to doses of isoproterenol, atropine, adenosine, lidocaine, and verapamil. The ER QRS was narrow (QRS < 120 ms) in 20 patients and wide (QRS > 120 ms) in 28 patients. Of the 28 patients with wide QRS ER, 11 patients had a new bundle branch block (8 patients new right bundle branch block [RBBB] and 2 patients new left bundle branch block [LBBB]). The ERCL was similar in both narrow and wide ERs (1,593 +/- 376 ms and 1,516 +/- 296 ms, P = 0.44). In 23 patients receiving isoproterenol infusion, the ER CL decreased with increasing doses from 1 mcg/min to 2 mcg/min (1,378 +/- 200 to 1,240 +/- 229 ms, P < 0.001), but did not decrease further at 3 mcg/min (1,201 +/- 192 ms, P = 0.48 vs 2 mg/min). Seven patients received 0.02 mg/kg of atropine, and ER decreased significantly (1,572 +/- 408 ms to 1,319 +/- 333 ms, P = 0.028). In 30 patients who received intravenous boluses of adenosine (6-18 mg), the ER did not change significantly. In 28 patients who received 150 mg of lidocaine, the ER increased from 1,462 +/- 286 ms to 1,715 +/- 467 ms (P < 0.001), and one patient developed transient asystole. Nineteen patients received 7.5 mg of verapamil, and the ER did not change (1,488 +/- 313 ms to 1,513 +/- 666 ms, P = 0.80). There was no significant difference in response to isoproterenol, adenosine, lidocaine, or verapamil between the patients with wide and narrow QRS ERs. We conclude that patients may have stable ERs immediately following AVJ ablation even when a wide complex ER results. The ER is responsive to sympathetic stimulation and vagal blockade. The ER is prolonged after lidocaine but not after verapamil, suggesting response to sodium but not to calcium channel blockade. These data are consistent with an ER originating in the distal compact AV node or proximal His bundle.

Transcoronary ethanol ablation of the atrioventricular node in a young patient with tricuspid atresia

Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter-based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.